Computers and Concrete, Vol. 14, No. 2 (2014) 193-209 DOI: http://dx.doi.org/10.12989/cac.2014.14.2.193 193 Copyright © 2014 Techno-Press, Ltd. http://www.techno-press.org/?journal=cac&subpage=8 ISSN: 1598-8198 (Print), 1598-818X (Online) Computer based estimation of backbone curves for hysteretic Response of reinforced concrete columns under static cyclic lateral loads M. Rizwan 1,2 , M.T.A. Chaudhary 3 , M. Ilyas 2 , Raja Rizwan Hussain 4 and T.R. Stacey 1 1 School of Mining Engineering, University of Witwatersrand, Johannesburg, South Africa 2 Department of Civil Engineering, University of Engineering & Technology, Lahore, Pakistan 3 Al Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi Arabia 4 Civil Engineering Department, College of Engineering, King Saud University, Riyadh, Saudi Arabia (Received February 17, 2014, Revised June 26, 2014, Accepted June 29, 2014) Abstract. Cyclic test of the columns is of practical relevance to the performance of compression members during an earthquake loading. The strength, ductility and energy absorption capabilities of reinforced concrete (RC) columns subjected to cyclic loading have been estimated by many researchers. These characteristics are not normally inherent in plain concrete but can be achieved by effectively confining columns through transverse reinforcement. An extensive experimental program, in which performance of four RC columns detailed according to provisions of ACI-318-08 was studied in contrast with that of four columns confined by a new proposed technique. This paper presents performance of columns reinforced by standard detailing and cast with 25 and 32 MPa concrete. The experimentally achieved load-displacement hysteresis and backbone curves of two columns are presented. The two approaches which work in conjunction with Response 2000 have been suggested to draw analytical back bone curves of RC columns. The experimental and analytical backbone curves are found in good agreement. This investigation gives a detail insight of the response of RC columns subjected to cyclic loads during their service life. The suggested analytical procedures will be available to the engineers involved in design to appraise the capacity of RC columns. Keywords: RC columns; hysteretic behaviour; computer based estimation; backbone curves; cyclic loading; performance simulation 1. Introduction Concrete has higher compressive strength but is brittle in nature. The confinement provided in reinforced concrete structural components introduces the properties of ductility, deformability and energy dissipation. These properties have important role to play in seismic performance of RC multistorey buildings. Sheikh S.M. (1978) recognizes that Considere in 1903 showed that axial capacity of a concrete column component can be increased by using spiral transverse reinforcement. Since then the researchers are focusing to quantify the contribution of confinement Corresponding author, Professor, E-mail: raja386@hotmail.com